Okay, I have a few questions about my amp. http://www.musiciansfriend.com/amplifiers-effects/acoustic-b450mkii-450w-bass-combo-amp 1) What does it mean by, "450 Watts (stand-alone), 600 Watts (w/extension speaker)?" 2) What in the heck is a, "High-Frequency horn driver with defeat switch?" 3) It says you can control the compressor and overdrive with a footswitch but I don't know how to do that. Do I need some additional hardware? Thanks for the help!